Line-of-sight velocities obtained with a bisector calculation for varying intensity levels of spectral lines synthesised from the MANCHA atmospheres. Left: velocities for non-degraded spectra synthesised at the simulation resolution. The degraded spectrum has undergone spatial and spectral blurring, was re-sampled to an instrumental spectral resolution, and was re-binned to different pixel sizes (see text for details). The curves for the different percentages of the line depth are offset by 2.5 km s⁻¹ for clarity. Dashed lines correspond to 0 km s⁻¹ for the different percentages of the line depth. Right: bisector velocities calculated from synthesised and degraded spectral profiles as in the left image, now shown for only two intensity levels with a spatial blurring employing a Gaussian of FWHM of 120 km (solid lines, same as in left panel) and an FWHM of 240 km (dashed lines). The curves for the different percentages of line depth are offset by 2.5 km s⁻¹ for clarity. The horizontal dashed lines correspond to 0 km s⁻¹ for the different percentages of the line depth.